Dark Carnival - Left 4 Dead 2
Intro to Dark Carnival
Having escaped from the shopping mall in the stock car, the group disembarks as the road ahead is blocked. To get to New Orleans, the ultimate objective, they need to pass through a carnival.
The UCI in this level are clowns. Their squeaking shoes attract other Infected so it is vital to take them out as quickly as possible. They also look pretty freaky. You should not see any until you enter the Carnival section.